Abstract/Project Summary Glial cells comprise approximately 80% of the cellular constituency of the adult central nervous system (CNS) and support a vast array of physiological roles essential to CNS function, including myelination, synapse formation, neurotransmission, and formation of the blood-brain barrier. Recent studies of glial development have documented many of the mechanisms that control the terminal differentiation and maturation of the astrocyte and oligodendrocyte sublineages. However, our knowledge of the preceding molecular processes that control the initiation of gliogenesis from multipotent neural stem cells in vivo remains rudimentary. The overriding goal of this proposal is to elucidate the molecular mechanisms that govern the initiation of gliogenesis. Recently we found that the Sox9/NFIA relationship represents a crucial regulatory node during neural stem cell commitment to the glial lineage, therefore dissection of their upstream regulatory events and downstream transcriptional networks will provide novel insight into the regulatory processes that control early gliogenesis. Our preliminary studies on the upstream regulatory events in gliogenesis suggest that Sox9 and Brn2 co-regulate NFIA through distinct enhancer elements that are brought together by Med12 mediated chromatin looping. Therefore in specific aim1 we will delineate how Brn2 regulates NFIA expression and whether Sox9/Brn2 collaboratively regulate NFIA induction and gliogenesis. In specific aim2, we will perform chromatin conformation capture (3C) to determine the three-dimensional architecture of the NFIA locus and examine whether the chromatin looping factor, Med12, regulates chromatin configuration at the NFIA locus and collaborates with Sox9/Brn2 to regulate NFIA induction. To identify key downstream events, we combined ChIP-Seq and gene expression profiling on FACS isolated, CD15+ spinal cord progenitors to dissociate the Sox9/NFIA transcriptional networks during gliogenesis. In specific aim3, we will validate and functionally analyze a set of candidate gliogenic targets identified in this screen and, in conjunction with our studies during gliogenesis, extend our ChIP-Seq analysis to earlier developmental stages to identify Sox9-specific targets in neural stem cell populations